The Incudostapedial Articulation in Down’s Syndrome (Trisomy 21): A Temporal Bone Study *Patricia Barcelos Ogando, †Christof Ro ¨o ¨sli, ‡Collin S. Karmody, and §Clarinda C. Northrop *Department of Otorhinolaryngology, Complexo Hospitalar Santa Casa de Porto Alegre, Porto Alegre, Brazil; ÞDepartment of Otorhinolaryngology, Head and Neck Surgery, University Hospital Zurich, Zurich, Switzerland; þDepartment of Otolaryngology, Tufts University School of Medicine; and §The Temporal Bone Foundation, Boston, Massachusetts, U.S.A. Hypothesis: Anomaly in the incudostapedial articulation (IS) may be responsible for persistent conductive hearing loss (HL) in Down’s syndrome (DS) patients. Our goal was to perform a detailed histopathologic assessment of the role of the IS joint in the conductive HL. Background: In addition to other disabilities, 38% to 78% of patients with Down’s syndrome (Trisomy 21) have CHL, some of which are persistent despite maximum treatment. The cause of the persistent conductive HL remains unclear. Methods: Retrospective analysis of temporal bone histopa- thology. Analyses of the midsection through the IS joint of 21 temporal bones (13 subjects) patients with DS and 31 tem- poral bones (18 subjects) from healthy subjects, performed by 2 blinded authors. The length of 7 different parameters of the width of the IS joint was measured and compared between the 2 groups. Results: The IS joint of patients with DS was significantly wider than the normal control. As opposed to the control, it did not decrease because of age. Conclusion: The persistent conductive HL in some patients with DS might be caused by anomaly of the IS joint. In severe cases, corrective surgery should be considered. Key Words: Conductive hearing lossVDown’s syndromeVIncudostapedial jointVTemporal bone histopathology. Otol Neurotol 34:1489Y1495, 2013. Down’s syndrome (DS, Trisomy 21) is a genetic dis- order with a prevalence of approximately one in 733 live births in the United States (1). The syndrome was first described by Esquirol in 1838 and Sequin in 1844 and more accurately defined by Down in 1866. In 1959, Lejeune and coworkers identified the classical karyotype of the syndrome (2). Hearing loss (HL) is one of the most frequent disabilities in DS, and it is estimated to affect 38% to 78% of this population (3,4). The majority of patients have conductive hearing losses supposedly re- lated to a high incidence of otitis media. However, nu- merous studies have found that frequently, the conductive hearing losses do not improve even after the insertion of tympanostomy tubes. The reason for this remains unclear (5,6). In an attempt to find the cause of this persistent conductive hearing loss, we investigated the ossicular chains in histologic sections of the temporal bones in patients with Down’s syndrome. This preliminary report focuses on the incudostapedial articulation/joint (Figs. 1 and 2) as a possible cause for conductive HL. The structurally intact incudostapedial (IS) joint is es- sential for audition. Miller and Keith, in a study of human temporal bones suggested that an elongated capsule al- lows motion of the incus without transmission of energy to the stapes (7). Most of the reported temporal bone studies in patients with DS paid attention to the inner ear, but the status of the ossicular joints has never been detailed in this population. The purpose of this study is to describe the comparative anatomy of the IS articulation in temporal bones from cases with the diagnosis of trisomy 21. MATERIALS AND METHODS The temporal bone collections at The Temporal Bone Foun- dation, Tufts University School of Medicine, The Massachussets Eye and Ear Infirmary, all in Boston, MA, and the Otitis Media Research Center in the Otolaryngology Department of the Address correspondence and reprint requests to Patricia Barcelos Ogando, M.D., Department of Otorhinolaryngology, Complexo Hospitalar Santa Casa de Porto Alegre, Rua Mostardeiro 333 sala 507YIndependencia, Porto Alegre-RSYBrazil, 90430-001; E-mail: patriciabogando@gmail.com The authors disclose no conflicts of interest. Otology & Neurotology 34:1489Y1495 Ó 2013, Otology & Neurotology, Inc. 1489 Copyright © 2013 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.